The electro-acoustic vibrating devices, ultrasonic devices or transducers are tools normally used for the realization of chemical manufacturing methods, of machinings by means of abrasive liquids or of weldings. According to their use a working frequency, usually near the resonance frequency of the ultrasonic device, can vary about between 16 and 100 KHz. For all of the applications it is important to define and to maintain during the working of the ultrasonic device working parameters and particularly the vibrating frequency, to values ensuring the best possible efficiency of the ultrasonic device.